Tagged Questions

Raster is a data format consisting of regular grids of values, usually stored in an image-like format.

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1
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2answers
134 views

Display Rectangular Data Grid

I'd like a Linux program which displays ASCII ArcGrid files (NxM rectangular ASCII data grids which may have either integer or floating point values). There is no practical upper or lower limit to ...
3
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1answer
517 views

Raster data array output flipped on x-axis using python/gdal?

I'm trying to create a raster using the python gdal libraries and I've gotten to the point where data is being output, but the output data is flipped on the origin point's x-axis. I know I must be ...
3
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2answers
914 views

Determine direction of rivers, which villages lie upstream and which downstream

I want to determine which villages lie upstream and which villages lie downstream big cities built on the side of rivers in Indonesia. I have the .shp file of villages and cities, the .shp file of all ...
3
votes
1answer
161 views

Change ellipsoid reference for altitude in a DEM

I have DEM data stored as RGF93 (Lambert-93) for lat/lon and NGF-IGN69 for altitude. I'm trying to change the reference ellipsoid for the elevation data (ultimately to NTF, but WGS84 would be fine to ...
11
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5answers
3k views

Get Raster Values from a Polygon Overlay in Opensource GIS Solutions

I have two layers. A polygon-shape-layer with many tiles and a raster-layer containing CORINE 2006 land cover with many categories in a colourmap. I want to obtain for each polygon in the shapelayer a ...
5
votes
3answers
694 views

Why is my mosaic of rasters a big, black rectangle?

I downloaded NED rasters from USGS, and I now want to mosaic all of the rasters into one. I used the Mosaic to New Raster tool, but the output is a big, black rectangle. Am I missing something? I feel ...
2
votes
1answer
334 views

Get raster field names in R

Does anyone know how I can extract the raster field names (VALUE, COUNT and other existing field names on a categorical raster file) in R? I am using the raster package to load the raster files.
4
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3answers
1k views

How to Clip a Vector File based on certain Raster Values?

I need to clip a vector file based on certain values of a raster (Slope > 2%). I can´t find a direct way to do it. Trying to vectorize the raster first didn´t work. Is there any tool (ArcGIS or ...
4
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3answers
605 views

Is there a “Tabulate Area” function in QGIS?

I have a raster file about land usage in northern italy (crops / urban areas ecc..) I have defined some buffer zones around some given points of a vector layer and I'd like to calculate the % of ...
1
vote
1answer
507 views

Preventing an Openlayers WMS layer from updating on zoom-change

I'm using openlayers to overlay a raster. When I zoom out, the overlaid layer expands to cover a larger area than was originally requested. I want the tile to be fixed to a particular boundary, and ...
2
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1answer
330 views

When creating a new raster, how to determine a raster's upperleftx, upperlefty?

I'd like to create a raster from point data, averaging the point data over a given area and placing the results into a given pixel/cell. With each pixel/cell as 50m x 50m. I'm new to this and have a ...
7
votes
3answers
5k views

How to calculate raster statistics for polygons?

how can I calculate sums, averages etc of raster-points (multi-band) per polygon of a vector-layer. I was told that this is called "zonal statistics". I tried that with QGIS first. There is a way to ...
1
vote
1answer
86 views

Which raster-format stores Missing, Strings, Variable Names, Multiple Bands

still looking for the ideal raster-format :-) GeoTiff stores: - projection/coordinate-system etc numerical values missing values multiple bands It does not allow for: variable-names. It just ...
3
votes
1answer
386 views

What are some examples of model-based upscaling of raster data?

Remotely-sensed raster data may be too fine-grained for many purposes. A typical approach to coarsen the grain is to upscale by reducing the resolution. If the data are continuous (e.g elevation, ...
7
votes
1answer
459 views

What are the rules that the Gdal rasterize function follows to allocate a value to a cell?

How does the rasterize tool decide which value to represent when a cell covers an area which inclueds different values? I need it in this case for polygons but would like to know for lines and points ...
3
votes
2answers
523 views

How to extract cell values from a raster file with Idrisi Taiga?

I need to convert raster cells into points. I use Idrisi and I need to generate a table containing xy (coordinates) and z (cell value).
1
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2answers
2k views

How to visualize grd files in Quantum GIS?

How to visualize grd files in the software Quantum GIS?
1
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2answers
1k views

Coordinates of raster image from .TAB file

I have got a raster image (tif) from a mapping site and an associated .TAB file. I am trying to correctly map it into CAD/3d model - which I know is set up to the correct coordinates. The .TAB file ...
2
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1answer
153 views

Creation raster image from interpolated image

I have interpolated temperature data that I have. This image's max and min values are 11.9 and -1.7, respectively. And then I exported this image to raster using 'export to raster'. But the max and ...
1
vote
1answer
324 views

Why can't r.patch find the rasters?

I have elevation rasters which loaded just fine in a GRASS session. They represent adjacent areas, so I want to meld them into one raster. I ran r.patch using the GRASS GUI, and it would only accept ...
2
votes
2answers
310 views

Is it possible to attain a classified raster with several classes in just one QGIS raster calculator operation?

I'm using qgis' raster calculator and wanted to make a new raster (oraster) from the values of an input raster (iraster). something like: if iraster>2 then oraster=1; if iraster >4 then oraster=2; ...
2
votes
1answer
579 views

How to change Datasource of a Raster in sde using ArcObjects?

I'm building a C# application that lets the user change their DataSources of all the layers in their MXD. I have it working on FeatureLayers and LYR files but I'm stuck on how to change Raster layers ...
3
votes
3answers
394 views

Georeferencing a whole heap of raster imagery

I have a whole heap of satelite imagery coming in that is not georeferenced. They have a grid overlaid so I do know the bounding box/coordinates of the images (and projection). I just need them ...
3
votes
2answers
4k views

How to export a raster layer for external processing?

Is there a way to export all values from a raster to for example a cvs or other textfile or dbf or xls and later import (changed) values from that file back into the raster? For vector-files this is ...
2
votes
2answers
2k views

How to exclude missing values from raster layer?

In my raster layers the value -999 means "missing". Those points completely mess up any colormap in qgis because qgis treats them as normal values and includes them in the classification. I would ...
6
votes
3answers
546 views

Suggestions for an efficient way to store raster files for lab use?

I'm trying to create a repository for our raster files from various sources and Im exploring the possibilities on how to store them and deliver them in our local intranet. I have come across rasdaman ...
0
votes
1answer
50 views

Does 'r.patch' act only on “loaded” rasters?

Can I run the GRASS command 'r.patch' on raster files which are not "loaded" into the current GRASS session? That is, rasters which are simply in my folder but not in a GRASS location & mapset? ...
10
votes
3answers
13k views

How to convert a vector layer to raster?

In qgis in the raster menu there is an item "convert vector to raster". This behaves strangely - I do not understand how it is supposed to work. I can select a vector file, an attribute and an ...
0
votes
2answers
377 views

Why does only one of three elevation rasters display correctly?

I downloaded a selected sub-set of the USGS National Elevation Data (NED) using their online GUI. This download came in the form of three files. The names of the files are 61471006, 61471006_2, and ...
0
votes
1answer
143 views

GRASS importing same-name rasters fails

I have NED elevation data in 3 rasters. (That's how it downloaded from USGS NED page.) The files are named "61471006", "61471006_2", and "61471006_3". I succeeded in using the GRASS GUI and menu ...
0
votes
1answer
544 views

How to work with OS map files from Digimap?

I am trying to add map tiles as raster files in QGIS but when I add them they all appear on top of each other. I did this once before and everything was ok but I am now unable to find how to get the ...
4
votes
3answers
3k views

How to combine information from raster and vector layers?

in QGIS I have 1 raster-layer (elevation) and 1 vector-layer (administrative units). Now I would like to be able to query one of the administrative units and see the mean and min/max of the elevation ...
0
votes
1answer
433 views

raster in TOC to geotiff on disk in ArcPy

I am really hoping that someone out there who knows a bit about ArcPy in ArcGIS10 can help me out. I am attempting to automate some work w/ netcdf files. Basically, I am able to automate the creation ...
4
votes
2answers
529 views

Is it possible to generate a vector polygon from a polygon on a raster image?

I have a raster map which I have extracted from a government report providing flood extent return frequencies. I want to 'snatch' these flood extent polygons (i.e. convert to vector) and I was ...
2
votes
1answer
104 views

Global composite of radar data available?

Iowa State offers an exceptional NEXRAD composite image as GeoTIFF for the entire continental US at a reasonable resolution. Is there a comparable GeoTIFF composite updated semi-regularly available ...
1
vote
1answer
616 views

How to convert Geostatistical analyst (GA) file to Raster FAST?

I have been trying to convert a number of Geostatistical analyst files that i were created using Geostatistical wizard in ArcGIS 10. I want to save these files as Raster and use the File Am i ...
0
votes
1answer
236 views

Plotting Smith and Sandwell global seafloor topography grids

Does anybody have any experience with plotting Smith & Sandwell 2-minute Mercator-projected grids in ArcGIS? I've downloaded one in two formats: ers and img. I've found tools for processing .img ...
1
vote
1answer
2k views

How can I extract raster values around points?

I'm using ArcMap 10. I have a point dataset and a .flt raster. For each point I want the sum of the raster values that lie within a certain radius of each point. i.e. I want to extract values within a ...
-1
votes
1answer
69 views

HOW to build a raster file from polygons showing subsoil layers classification?

I'm trying to build a raster map showing different subsoil features for a further analysis in ModFlow. I wonder how I can build a raster which shows different subsoil features?
1
vote
1answer
237 views

PostGIS Raster convolution filters

I've looked through the PostGIS raster documentation, but can't find an indication of how to apply a convolution filter to raster data. Does this capability even exist (yet?) There only appears to be ...
6
votes
2answers
2k views

How do I layer stack rasters in QGIS?

I have some multi-spectral data, where the individual bands are separate Raster files. How do I layer stack these rasters so that I get one raster with 3 bands instead of 3 different rasters? This ...
5
votes
2answers
4k views

How to clip a vector feature to the extent of an existing raster dataset using arcpy

I have a clipped raster dataset with polylines (from the contour tool) overlayed (see attached). I am trying to clip the polylines to the extent of the raster dataset, which seems simple enough, but ...
1
vote
2answers
689 views

Mosaicing LIDAR files in ArcGIS 10

I have a number of LIDAR files (the extension is .adf). When put together, they show the same area (each shows one part of it), so, before I do anything else with them, I would like to combine them ...
3
votes
1answer
194 views

Efficiently classify raster with irregular polygons

I have a project on my desk to classify an elevation model using different elevation breaks for each polygon in the area of interest. In pseudo code: FOR each polygon IN layer: CREATE_MASK FROM ...
2
votes
0answers
99 views

raster data expressed as percent

I downloaded NDVI greeness data from the USGS Integrated Vegetation Mapping Viewer. In the metadata it says that visual greenness values range from 0 to 100. My data is from the period ending 3/5/12 ...
8
votes
7answers
13k views

Get boundary of raster image as polygon in ArcGIS 10

I have a rectangular raster image in ArcGIS. My question is: how can I produce a polygon which is just the extent of the raster image? That is, I want to have a polygon layer with a single ...
2
votes
0answers
225 views

Importing Rasters to ArcSDE 9.3.1 using sderaster

OK, I am trying to import a raster to 11g using the sderaster command. It is a stand alone jpg with a world file associated, and pyramids. Am I right in assuming I cannot import a JPG, I can only ...
2
votes
1answer
113 views

Can Identify tool to return the raw values of rasters?

I have a raster in ArcGIS 10 SP4 set to bilinear resampling in its display properties. When using the identify tool it returns the resampled value instead of the raw value. Can we get the identify ...
1
vote
1answer
409 views

OpenLayers ArcGIS Image Service Support

i have ArcGIS Image Server for publishing my raster data to my user. In traditionally way i have been tiling with gdal and it takes a long time besides this it requires more effort for getting true ...
0
votes
1answer
173 views

Progress bar percentage is increasing and decreasing, never finishing

I am trying to clip a raster by shapefile perimeter using the Clip tool. The percentage has been jumping between 0% and 100% for over an hour, back and forth, climbing to 100% then dropping down to ...